DESCRIPTION: With increasing age, median hearing thresholds insidiously deteriorate to such an extent that late onset, progressive hearing impairment is the most common neurological disability of the elderly. Although hearing loss of at least 25 decibels (dB) is present in only 1% of young adults between 18-24 years of age this figure increases to 10% in individuals between 55-64 years of age and to approximately 50% in octogenarians. The relative contribution of heredity to age-related hearing impairment is not known, however the majority of inherited late-onset hearing loss appears to be autosomal dominant and non-syndromic. In several large families in which this type of impairment is segregating, linkage analysis has been used to localize the relevant genes. To date, thirteen different genes responsible for autosomal dominant non- syndromic hearing loss (ADNSHL) have been localized; only one has been cloned. The specific aims of this proposal are to localize additional genes from ADNSH in appropriately studied large kindreds; to clone candidate genes for DFNA10 and DFNA13; to demonstrate mutations in these candidate genes; and, to offer genetic counseling to families with DFNA4, DFNA10, and DFNA13. By localizing many of the relevant ADHSHL genes and cloning the more common ones, this research will lead to better understanding of progressive, late-onset hereditary hearing impairment in the United States. This knowledge will foster the development of studies in gene- gene interactions, gene environment interactions, and ultimately, therapeutic intervention to prevent progression of some forms of hearing impairment.